English

Etymology

Back-formation
termites was the three-syllable plural of termes but the singular
was lost, the plural given two syllables, and now we have termite
and termites. From Latin termes, as in 'terminal', meaning those
that terminate, or destroy. Also possible a derivation from
proto-indoeuropean root term-, drill (insect that drills or
excavates galleries).

Termites, sometimes incorrectly called "white
ants", are a group of
socialinsects usually classified at the
taxonomic
rank of order
Isoptera (but see also taxonomy below).
As truly social animals, they are termed eusocial along with the ants
and some bees and wasps. Termites mostly feed on dead plant material, generally
in the form of wood, leaf litter, soil, or animal dung, and about
10% of the estimated 4,000 species (about 2,600 taxonomically
known) are economically significant as pests that can cause serious
structural damage to buildings, crops or plantation forests.
Termites are major detrivores, particularly in
the subtropical and
tropical
regions, and their recycling of wood and other plant matter is of
considerable ecological importance.

As eusocial
insects, termites live in colonies that, at maturity, number
from several hundred to several million individuals. They are a
prime example of decentralised, self-organised
systems using swarm
intelligence and use this cooperation to exploit food sources
and environments that could not be available to any single insect
acting alone. A typical colony contains nymphs (semi-mature young),
workers, soldiers, and reproductive individuals of both genders,
sometimes containing several egg-laying queens.

Social organization

Reproductives

A female that has flown, mated, and is
producing eggs, is called a "queen". Similarly, a male that has
flown, mated, and remains in proximity to a queen, is termed a
"King". These anthropocentric terms have caused great
misunderstanding of colony dynamics. Research using genetic
techniques to determine relatedness of colony members is showing
that the idea that colonies are only ever headed by a monogamous royal pair is
wrong. Multiple pairs of reproductives within a colony are not
uncommon. In the families Rhinotermitidae and Termitidae, and
possibly others, sperm
competition does not seem to occur (male genitalia are very simple and
the sperm are anucleate), suggesting that only one male (king)
generally mates within the colony.

At maturity, a primary queen has a great capacity
to lay eggs. In physogastric species, the
queen adds an extra set of ovaries with each moult, resulting in a greatly
distended abdomen and
increased fecundity,
often reported to reach a production of more than two-thousand eggs
a day. The distended abdomen increases the queen's body length to
several times more than before mating and reduces her ability to
move freely, though attendant workers provide assistance. The queen
is widely believed to be a primary source of pheromones useful in colony
integration, and these are thought to be spread through shared
feeding (trophallaxis).

The king grows only slightly larger after initial
mating and continues to mate with the queen for life. This is very
different from ant colonies, in which a queen mates once with the
male(s) and stores the gametes for life, and the male
ants die shortly after mating.

The winged (or 'alate') caste, also referred to
as the reproductive caste, are generally the only termites with
well-developed eyes (although workers of some harvesting species do
have well-developed compound eyes, and, in other species, soldiers
with eyes occasionally appear). Termites on the path to becoming
alates (going through incomplete
metamorphosis) form a sub-caste in certain species of termites,
functioning as workers ('pseudergates') and also as potential
supplementary reproductives. Supplementaries have the ability to
replace a dead primary reproductive and, at least in some species,
several are recruited once a primary queen is lost.

In areas with a distinct dry season, the alates
leave the nest in large swarms after the first good soaking rain of
the rainy season. In other regions, flights may occur throughout
the year or more commonly in the spring and autumn. Termites are
relatively poor fliers and are readily blown downwind in windspeeds
of less than 2 kph,
shedding their wings soon after landing at an acceptable site,
where they mate and attempt to form a nest in damp timber or
earth.

Workers

Worker termites undertake the labours of foraging,
food storage, brood, nest maintenance, and some of the defence
effort in certain species. Workers are the main caste in the colony
for the digestion of cellulose in food and are the
most likely to be found in infested wood. This is achieved in one
of two ways. In all termite families except the Termitidae, there
are flagellateprotists in the gut that
assist in cellulose digestion. However, in the Termitidae, which
account for approximately 60% of all termite species, the
flagellates have been lost and this digestive role is taken up, in
part, by a consortium of prokaryotic organisms. This
simple story, which has been in Entomology
textbooks for decades, is complicated by the finding that all
studied termites can produce their own cellulaseenzymes, and therefore can digest
wood in the absence of their symbiotic microbes. Our knowledge of
the relationships between the microbial and termite parts of their
digestion is still rudimentary. What is true in all termite
species, however, is that the workers feed the other members of the
colony with substances derived from the digestion of plant
material, either from the mouth or anus. This process of feeding of
one colony member by another is known as trophallaxis and is one of
the keys to the success of the group. It frees the parents from
feeding all but the first generation of offspring, allowing for the
group to grow much larger and ensuring that the necessary gut
symbionts are transferred from one generation to another.

Termite workers are generally blind due to
undeveloped eyes. Despite this limitation, they are able to create
elaborate nests and tunnel systems using a combination of soil,
chewed wood/cellulose, saliva, and faeces. Some species have been
known to create such durable walls that industrial machinery has
been damaged in an attempt to break their tall mounds. Some African
and Australian species have mounds more than 4 metres high. The
nest is created and maintained by workers with many distinct
features such as housing the brood, water collection through
condensation, reproductive chambers, and tunnel networks that
effectively provide air conditioning and control the CO2/O2
balance. A few species even practice agriculture, with elaborate
fungal gardens which are fed on collected plant matter, providing a
nutritious mycelium on
which the colony then feeds (see "Diet", below).

Soldiers

The soldier caste has anatomical and behavioural
specializations, providing strength and armour which are primarily
useful against ant attack. The proportion of soldiers within a
colony varies both within and among species. Many soldiers have
jaws so enlarged that they cannot feed themselves, but instead,
like juveniles, are fed by workers. The pan-tropical sub-family
Nasutitermitinae (which should probably have the South American
species separated) have soldiers with the ability to exude noxious
liquids through either a horn-like nozzle (nasus) or simple hole in
the head (fontanelle). Fontanelles
which exude defensive secretions are also a feature of the family
Rhinotermitidae. Many species are readily identified using the
characteristics of the soldiers' heads, mandibles, or nasus. Among the
drywood termites, a soldier's globular ("phragmotic") head can be
used to block their narrow tunnels. Termite soldiers are usually
blind, but in some families, soldiers developing from the
reproductive line may have at least partly functional eyes. It's
generally accepted that the specialization of the soldier caste is
principally a defence against predation by ants. The wide range of
jaw types and phragmotic heads provides methods which effectively
block narrow termite tunnels against ant entry. A tunnel-blocking
soldier can rebuff attacks from many ants. Usually more soldiers
stand by behind the initial soldier so once the first one falls
another soldier will take the place. In cases where the intrusion
is coming from a breach that is larger than the soldier's head,
defence requires special formations where soldiers form a phalanx-like
formation around the breach and blindly bite at intruders or shoot
toxic glue from the nasus.
This formation involves self-sacrifice because once the workers
have repaired the breach during fighting, no return is provided,
thus causing the death of all the defenders.

Termites undergo incomplete metamorphosis,
with their freshly hatched young taking the form of tiny termites
that grow without significant morphological changes (other than
wings and soldier specializations). Some species of termite have
dimorphic soldiers (up
to three times the size of smaller soldiers). Though their value is
unknown, speculation is that they may function as an elite class
that defends only the inner tunnels of the mound. Evidence for this
is that, even when provoked, these large soldiers do not defend
themselves but retreat deeper into the mound. On the other hand,
dimorphic soldiers are common in some Australian species of
Schedorhinotermes that neither build mounds nor appear to maintain
complex nest structures. Some termite taxa are without soldiers;
perhaps the best known of these are the Apicotermitinae.

Diet

Termites are generally grouped according to their
feeding behaviour. Thus, the commonly used general groupings are
subterranean, soil-feeding, drywood, dampwood, and grass-eating. Of
these, subterraneans and drywoods are primarily responsible for
damage to human-made structures.

All termites eat cellulose in its various forms
as plant fibre. Cellulose is a rich energy source (as demonstrated
by the amount of energy released when wood is burned), but remains
difficult to digest. Termites rely primarily upon symbiotic
protozoa (metamonads)
such as Trichonympha,
and other microbes in
their gut to digest the cellulose for them and absorb the end
products for their own use. Gut protozoa, such as Trichonympha,
in turn rely on symbiotic bacteria embedded on their
surfaces to produce some of the necessary digestive enzymes. This
relationship is one of the finest examples of mutualism among
animals. Most so called "higher termites", especially in the
Family
Termitidae, can produce their own cellulase enzymes. However,
they still retain a rich gut fauna and primarily rely upon the
bacteria. Due to closely related bacterial species, it is strongly
presumed that the termites' gut flora are descended from the gut
flora of the ancestral wood-eating cockroaches, like those of the
genus Cryptocercus.

Some species of termite practice fungiculture. They maintain
a 'garden' of specialized fungi of genus Termitomyces,
which are nourished by the excrement of the insects. When the fungi
are eaten, their spores pass undamaged through the intestines of
the termites to complete the cycle by germinating in the fresh
faecal pellets. They are also well known for eating smaller insects
in a last resort environment.

Mounds

Human interaction

Because of their wood-eating habits,
termites sometimes do great damage to buildings and other wooden
structures. Their habit of remaining concealed often results in
their presence being undetected until the timbers are severely
damaged and exhibit surface changes. Once termites have entered a
building, they do not limit themselves to wood; they also damage
paper, cloth, carpets, and other cellulosic
materials. Often, other soft materials are damaged and may be used
for construction. Particles taken from soft plastics, plaster,
rubber, and sealants such as silicon rubber and acrylics are often
employed in construction.

Termites usually avoid exposure to unfavourable
environmental conditions. They tend to remain hidden in tunnels in
earth and wood. Where they need to cross an impervious or
unfavourable substrate, they cover their tracks with tubing made of
faeces, plant matter, and soil. Sometimes these shelter tubes will
extend for many metres, such as up the outside of a tree reaching
from the soil to dead branches. Termite barrier systems used for
protecting buildings aim to prevent concealed termite access, thus
forcing the termites out into the open where they must form clearly
visible shelter tubes to gain entry.

Termites can be major agricultural pests,
particularly in Africa and Asia, where crop losses can be severe.
Counterbalancing this is the greatly improved water infiltration
where termite tunnels in the soil allow rainwater to soak in deeply
and help reduce runoff and consequent soil erosion.

In many cultures, termites are used for food
(particularly the alates), and termite nests are used widely in
construction (the dirt is often dust-free) and as a soil
amendment.

Humans have moved many wood-eating species
between continents, but have also caused drastic population decline
in others through habitat loss and pesticide application.

Avoiding termite troubles

Precautions:

Avoid contact of susceptible timber with ground by using
termite-resistant concrete, steel, or masonry foundation with
appropriate barriers. Even so, termites are able to bridge these
with shelter tubes, and it has been known for termites to chew
through piping made of soft plastics and even some metals, such as
lead, to exploit moisture. In general, new buildings should be
constructed with embedded physical termite barriers so that there
are no easy means for termites to gain concealed entry. While
barriers of poisoned soil, so called termite
pre-treatment, have been in general use since the 1970s, it is
preferable that these be used only for existing buildings without
effective physical barriers.

The intent of termite barriers (whether physical, poisoned
soil, or some of the new poisoned plastics) is to prevent the
termites from gaining unseen access to structures. In most
instances, termites attempting to enter a barriered building will
be forced into the less favourable approach of building shelter
tubes up the outside walls, and thus, they can be clearly visible
both to the building occupants and a range of predators. Regular
inspection by a competent (trained and experienced) inspector is
the best defence.

Use of timber that is naturally resistant to termites such as
Canarium australianum (Turpentine Tree), Callitris glaucophylla
(White Cypress), or one of the Sequoias. Note that there is no tree
species whose every individual tree yields only timbers that are
immune to termite damage, so that even with well known
termite-resistant timber types, there will occasionally be pieces
that are attacked.

When termites have already penetrated a building,
the first action is usually to destroy the colony with insecticides before removing
the termites' means of access and fixing the problems that
encouraged them in the first place. Baits (feeder stations) with
small quantities of disruptive insect hormones or other very slow
acting toxins have become the preferred least-toxic management tool
in most western countries. This has replaced the dusting of toxins
direct into termite tunnels that had been widely done since the
early 1930s (originating in Australia). The main dust toxicants
have been the inorganic metallic poison arsenic
trioxide, insect growth regulators (hormones) such as Triflumuron
and, more recently, fipronil. Blowing dusts into
termite workings is a highly skilled process. All these slow-acting
poisons can be
distributed by the workers for hours or weeks before any symptoms
occur and are capable of destroying the entire colony. More modern
variations include chlorfluazuron, Diflubenzuron,
hexaflumuron, and
Novaflumuron as bait toxicants and fipronil and imidacloprid as soil
poisons. Soil poisons are the least-preferred method of control as
this requires much larger doses of toxin and results in
uncontrollable release to the environment.

Termites in the human diet

The alates are nutritious,
having a good store of fat and protein, and are palatable in most
species with a nutty flavour when cooked. They are easily gathered
at the beginning of the rainy season in Central
and Southern
Africa when they swarm, as they are attracted to lights and can
be gathered up when they land on nets put up around a lamp. The
wings are shed and can be removed by a technique similar to
winnowing. They are
best gently roasted on a hot plate or lightly fried until slightly
crisp; oil is not
usually needed since their bodies are naturally high in oil.
Traditionally they make a welcome treat at the beginning of the
rainy season when livestock is lean, new crops have not yet
produced food, and stored produce from the previous growing season
is running low.

Ecology

Ecologically, termites are important in nutrient recycling, habitat
creation, soil formation
and quality and, particularly the winged reproductives, as food for
countless predators.
The role of termites in hollowing timbers and thus providing
shelter and increased wood surface areas for other creatures is
critical for the survival of a large number of timber-inhabiting
species. Larger termite mounds play a role in providing a habitat
for plants and animals, especially on plains in Africa that are
seasonally inundated
by a rainy
season, providing a retreat above the water for smaller animals
and birds, and a growing medium for woody shrubs with root systems
that cannot withstand inundation for several weeks. In addition,
scorpions, lizards, snakes, small mammals,
and birds live in abandoned or weathered mounds, and aardvarks dig substantial caves
and burrows in them, which then become homes for larger animals
such as hyenas and
mongooses.

As detrivores, termites clear
away leaf and woody litter and so reduce the severity of the annual
bush fires in African savannas, which are not as destructive as
those in Australia and the USA.

Globally, termites are found roughly between 50
degrees North & South, with the greatest biomass in the tropics and the
greatest diversity in tropical forests and Mediterranean
shrublands. Termites are also considered to be a major source of
atmospheric methane, one
of the prime greenhouse
gases. Termites have been common since at least the Cretaceous
period. Termites also eat bone and other parts of carcasses, and
their traces have been found on dinosaur bones from the middle
Jurassic in China.

Plant defences against termites

Many plants have developed
effective defences against termites, and in most ecosystems, there is an
observable balance between the growth of plants and the feeding of
termites. Defence is typically achieved by secreting anti-feedant
chemicals (such as oils,
resins, and lignins) into the woody cell
walls. This reduces the ability of termites to efficiently digest
the cellulose. Many of
the strongly termite-resistant tree species have heartwood timber that is
extremely dense (such as Eucalyptus
camaldulensis) due to accretion of these resins. Over the years
there has been considerable research into these natural defensive
chemicals with scientists seeking to add them to timbers from
susceptible trees. A commercial product, "Blockaid", has been
developed in Australia and uses a range of plant extracts to create
a paint-on nontoxic termite barrier for buildings. In 2005, a group
of Australian scientists "discovered" (announced) a treatment based
on an extract of a species of Eremophila
that repels termites. Tests have shown that termites are strongly
repelled by the toxic material to the extent that they will starve
rather than cross treated samples. When kept in close proximity to
the extract, they become disoriented and eventually die. Scientists
hope to use this toxic compound commercially to prevent termite
feeding.

Taxonomy, evolution and systematics

Recent DNA evidence has
supported the nearly 120-year-old hypothesis, originally based on
morphology, that termites are most closely related to the
wood-eating cockroaches (genus Cryptocercus),
to which the singular and very primitive Mastotermes
darwiniensis shows some telltale similarities. Most recently,
this has led some authors to propose that termites be reclassified
as a single family, Termitidae, within the order Blattaria, which
contains cockroaches . However, most researchers advocate the less
drastic measure of retaining the termites as Isoptera but as a
group subordinate to true roaches, preserving the internal
classification of termites .

Evolutionary history

The oldest unambiguous termite
fossils date to the
early Cretaceous,
although structures from the late Triassic have been interpreted as
fossilized termite nests. Given the diversity of Cretaceous
termites, it is likely that they had their origin at least sometime
in the Jurassic.

It has long been accepted that termites are
closely related to cockroaches and mantids, and they are classified
in the same superorder (Dictyoptera),
but new research has shed light on the details of termite
evolution. There is now strong evidence suggesting that termites
are really highly modified, social, wood-eating cockroaches. A
study conducted by scientists has found that endosymbiotic bacteria
from termites and a genus of cockroaches, Cryptocercus,
share the strongest phylogenetical similarities out of all other
cockroaches. Both termites and Cryptocercus also share similar
morphological and social features -- most cockroaches do not show
social characteristics, but Cryptocercus takes care of its young
and exhibits other social behaviour. As mentioned above, the
primitive Giant
Northern Termite (Mastotermes darwiniensis) exhibits numerous
cockroach-like characteristics that are not shared with other
termites.

Termites are capable of producing up to two
litres of hydrogen from fermenting a single sheet of paper, making
them one of the planet's most efficient bioreactors. Termites
achieve this high degree of efficiency by exploiting the metabolic
capabilities of about 200 different species of microbes that
inhabit their hindguts.

Hydrogen is normally created by using electricity
to remove hydrogen molecules from water or natural gas, but the
electricity is most often generated using fossil fuels that emit
carbon pollutants. The microbial community in the termite gut
efficiently manufactures large quantities of clean hydrogen. By
sequencing the termite's
microbial community, it may be possible to get a better
understanding of these biochemical pathways.

Termites eat wood but cannot extract energy from
the complex lignocellulose polymers within it. These polymers are
broken down into simple sugars by fermenting bacteria in the
termite's gut and using enzymes that produce hydrogen as a
byproduct. A second wave of bacteria uses the simple sugars and
hydrogen to make the acetate the termite requires for energy. If it
can be determined which enzymes are used to create hydrogen, and
which genes produce them, this process could be scaled up with
bioreactors to
generate hydrogen from woody biomass, such as poplar, in commercial
quantities.

Sceptics regard this as unlikely to be a
carbon-neutral commercial process due to the energy inputs. For
decades, researchers have sought to house termites on a commercial
scale (like worm farms) to
break down woody debris and paper but funding has been scarce and
the problems of developing a continuous process that does not
disrupt the termites' homeostasis have not been
overcome.